Equipment

Yet Another Post About My Issues With UV Filters

This is a good filter. It is NOT the filter that was returned with the lens in question. Roger Cicala

Yes, I’m sick of filter articles, too. But I come today not to educate you, but to mock others. Because yes, people continue to try to save a few bucks by putting a cheap filter in front of their $1,000 lens. And also because they buy what they think are good filters off of Fleabay or some used place and these filters aren’t what they think. This can particularly happen when you purchase a brand that makes different filters of differing quality.

How bad can it be, you ask? Well, today we’ll show you. Because someone had a 70-200mm f/2.8 lens that had been nice and sharp and then returned it because it suddenly got soft. They were kind enough to return it with their protective filter in place.

So the first thing we did, as we always do, was put the lens on OLAF, which is simply an array of collimated 5-micron pinholes. A good lens should show and an array of small dots or circles. But this lens showed an array of glaring star flare thingies.

200mm with the filter in place. Olaf Optical Testing, 2017

No question, the customer was right, images from that lens had to be soft. But, just for completeness, we removed the filter, even though its label indicated it was a high-quality filter. Without the filter, it looked just like it should have.

200mm without the filter. Olaf Optical Testing, 2017

Another thing we do on OLAF is slightly defocusing the image. In a nicely centered lens, the dots should turn into regular circles. This is that same lens above, just slightly defocused and looking just like we’d expect.

Olaf Optical Testing, 2017

Then we put the filter back on without changing anything else.

Olaf Optical Testing, 2017

If you have the slightest bit of visual imagination, you can probably figure out that there would be some bizarre, ugly bokeh with the filter on this lens. If you’re an optical geek, you might think that perhaps this filter isn’t really flat optical glass, it’s cheap sheet glass with a bit of wavy thickness.

There are a couple of things I should mention, just for completeness. We repeated the test with other copies of the same lens using the customer’s filter, and the results were identical. We also put a high-quality filter on the client’s lens and while there was a bit of blurring of the pinholes (longer lenses are more sensitive to filters), it was very minor.

So, if you want to know how much a filter that looks shiny and clear when you look through it can affect your images if it’s a cheap POS, well, there you go. Because if you looked at this filter, and looked through this filter, it would look just fine.

And another caution, just because a filter has a name brand on the side you recognize doesn’t mean it’s a good filter. For example, you can buy Tiffen or Hoya brand 77mm protective filters for $15-$18, or a better quality one of the same brand for about $35 , or top-quality for $70+ at a reputable dealer. The $15 filter is not the same quality as the $70 even though they both have the same brand on the side. And if you buy from less reputable dealers all bets are off because knock off cases for the higher priced filters are easy to obtain and the filter inside might not be what you think it is.

To learn more about what I think about UV filters in general, read my article on the topic here. There are circumstances where good-quality UV or clear filters are really a good idea. But there are no circumstances where a low-quality filter is a good idea. None.

Roger Cicala and Aaron Closz

Lensrentals.com

May, 2017

Author: Roger Cicala

I’m Roger and I am the founder of Lensrentals.com. Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Its soooo simple. Too much time wasted (mine to). I agree with Shield Block. Buy a quality (Hoya B+W) filter and test it out. That’s what I do and have never lost picture after I determined the filter was fine, no IQ effects. I also keep the front clean. When you are a little anal, like me with cleaning, a filter that does not hurt IQ that I can see is better than rubbing the expensive front element of a lens over time; especially over time. I don’t use filters on my weather resistant lens that have a special coating to repel water. Other than that…

First, I’m with the guy that thanks you for the empirical evidence (turning to your original article now). Second – I looked at the OLAF images and wondered if there is a creative way to use the cheap-filter effect… (laugh).

Brandon Dube

my point is that the filter requires about a fifth of a pound of optical glass to manufacture, which will cost about $2 per filter. Grinding and polishing a precision flat at volume has nearly zero cost, and the coating will be << $10 at volume, likely < $1.

There are few glass manufactures – outside of exotics you will only see Schott, Ohara, Hoya, and Corning. I do not think you worked at a glass manufacture in a technical or production role from reading your comment.

Robson Robson

Hello Jeff, LEDs typically have viewing angles large enough so that you shouldn’ t be blinded. And if they have large enough a viewing angle they tend to be not laser diodes.
So you don’ t have to look into a laser with your remaining eye to check your filter… 😉

Mike Barrett

ok, I guess…… Even IF it takes 1-5lbs of glass per filter I think is your point?

Dmitry Anisimov

Of course. 200 mm is telephoto. The same filter wouldn’t have been a problem on a 21 mm lens xD

Michael Clark

Because that really thin, flat filter made out of BK-7 is just as strong and resistant to shattering as that 3/4 inch thick piece of curved, higher grade glass called the front element, right?

And as you discovered, the greatest concern about impact damage is to internal alignment of lens elements and other internal moving parts.

Brandon Dube

I very strongly doubt they test the surface quality of every filter adequately. To do that you need an interferometer, the setup for which will cost a quarter million dollars. You don’t use a $250k machine to test $25 filters.

You wouldn’t (and can’t) MTF test a filter, since it isn’t image forming.

They may spectrally test every filter, but that would be outside the norm. Typically one sample flat is taken from each coating run and taken to be representative of all of them.

Tilting a filter that is truly flat on both sides won’t do anything for a subject very far away.

Ed Hassell

I live in northeastern NC on the Albemarle sound — beautiful, but the middle of nowhere. Soil is either sand or clay or black mud. In the summer, humidity is 110% on a dry day; so, anything that touches the lens sticks. Sometimes, I just change filters and clean later.

Lewis Johnson

Thanks for reporting this.
I was going ask if slow or inaccurate was a theoretical issue after seeing the OLAF images above. Af, particularly contrast af isn’t going to like the funky flare.

Eeseekeal Flamthrower

My opinion is that if a photographer shoots in messy situations where it might not be easy to protect the lens/camera then a filter makes sense. Also, on many lenses, the lens is not deemed ‘sealed’ unless a filter is in place. I take care to protect my gear, mostly shoot in the dry desert, and I’m not a pro with heavy duty usage. I don’t use a filter, and I don’t have any scratches or wear on my front elements. I also ALWAYS use a hood.

Notna

Great, it’ll be interesting to see just how big the difference is between a crap filter and a decent or good one.

Jesse Lee

I applaud your stubborn stubbornness. Bravo. Well done.

Seriously, did I “refuse to acknowledge that blah blah blah”? Did I say ANYTHING remotely close to it? I asked ONE question and you go all Webster on me, and now I”m the one who’s at fault? Seriously?

I was challenging the OP that not putting on filters puts his lenses at risk, and thus he’s likely to replace lenses often. You’re the one who refuses to even read at the most basic level. I myself use filters and have rarely had to replace one, except for the two that were cracked when shooting in hectic scenes. How the hell did you arrive at me “refusing to concede that blah blah blah replace filters”??? ONE question, and you were able to derive all that. Keep up the good work. No wait, don’t.

And yes, upvotes are the qualifiers of life. I really envy all five of your upvotes. Only 95 left till 100!

Jeff Allen

Sometimes things need to be set in context. Roger mentions most scratches will not photograph shooting into the light on front elements. This is also true of good quality filters including resin filters that some people have an issue with. Resin filters made well use the same optical quality resin used in glasses such as Acomon AG Rav 7 and are pressed between ground & polished steel sheets carefully aligned, whilst the filter is still warm from dyeing.
They undergo flatness testing, MTF readings and spectrometer testing EVERY filter.
All that said Panavision make a filter holder that tilts the filter slightly to minimise veiling glare shooting into the light, those images are projected far larger than most stills images and whilst we do not dwell on single movie frames none the less focus is often critical.
Filters have a place, they are not ideal but sometimes they save an otherwise mundane shot and artistically can transform a scene (think reflections on water, over bright skies, boosting blue skies etc)

Jeff Allen

Then after years of doing this wonder why your eye sight has degraded. Small point source LEDs are very bad for the rear of your eye you should never look at LEDs without them being diffused.

El Aura

Well, B refuses to acknowledge the simple fact that whatever destroys a lens front element would also destroy any filter on it. Thus any camera usage that leads to X destroyed lens front elements also leads to X destroyed filters.

B also assumes that most people have many of such events (without ‘many’ of such events, there wouldn’t be ‘often’ lens replacements). But B refuses to concede that only people which often need to replace filters would often need to replace a lens front element if they didn’t wear filters. Why that is so remains a mystery.

B should also contend with the fact C’s post got five upvotes while B’s posts got zero upvotes.